{"id":14278,"date":"2019-12-12T16:42:21","date_gmt":"2019-12-13T00:42:21","guid":{"rendered":"https:\/\/www.darkenergybiosphere.org\/?post_type=publication&#038;p=14278"},"modified":"2019-12-12T16:42:22","modified_gmt":"2019-12-13T00:42:22","slug":"methane-sources-and-sinks-in-continental-sedimentary-systems-new-insights-from-paired-clumped-isotopologues-13ch3d-and-12ch2d2","status":"publish","type":"publication","link":"https:\/\/www.darkenergybiosphere.org\/publication\/methane-sources-and-sinks-in-continental-sedimentary-systems-new-insights-from-paired-clumped-isotopologues-13ch3d-and-12ch2d2\/","title":{"rendered":"Methane sources and sinks in continental sedimentary systems: New insights from paired clumped isotopologues 13CH3D and 12CH2D2"},"content":{"rendered":"<p id=\"sp0005\">Stable isotope\u00a0compositions of\u00a0methane\u00a0(\u03b4<sup>13<\/sup>C and \u03b4D) and of short-chain\u00a0alkanes\u00a0are commonly used to trace the origin and fate of carbon in the\u00a0continental crust. In continental sedimentary systems, methane is typically produced through thermogenic cracking of organic matter and\/or through microbial\u00a0methanogenesis. However, secondary processes such as mixing, migration or\u00a0biodegradation\u00a0can alter the original isotopic and composition of the gas, making the identification and the quantification of primary sources challenging. The recently resolved methane \u2018clumped\u2019 isotopologues \u0394<sup>13<\/sup>CH<sub>3<\/sub>D and \u0394<sup>12<\/sup>CH<sub>2<\/sub>D<sub>2<\/sub>\u00a0are unique indicators of whether methane is at thermodynamic isotopic equilibrium or not, thereby providing insights into formation temperatures and\/or into kinetic processes controlling methane generation processes, including microbial methanogenesis.<\/p>\n<p id=\"sp0010\">In this study, we report the first systematic use of methane \u0394<sup>13<\/sup>CH<sub>3<\/sub>D and \u0394<sup>12<\/sup>CH<sub>2<\/sub>D<sub>2<\/sub>\u00a0in the context of continental\u00a0sedimentary basins. We investigated sedimentary formations from the Southwest Ontario and Michigan Basins, where the presence of both microbial and thermogenic methane was previously proposed. Methane from the\u00a0Silurian\u00a0strata\u00a0coexist with highly saline brines, and clumped isotopologues exhibit large offsets from\u00a0thermodynamic equilibrium, with \u0394<sup>12<\/sup>CH<sub>2<\/sub>D<sub>2<\/sub>\u00a0values as low as \u221223\u2030. Together with conventional \u03b4<sup>13<\/sup>C and \u03b4D values, the variability in \u0394<sup>13<\/sup>CH<sub>3<\/sub>D and \u0394<sup>12<\/sup>CH<sub>2<\/sub>D<sub>2<\/sub>\u00a0to first order reflects a mixing relationship between near-equilibrated thermogenic methane similar to gases from deeper Cambrian and\u00a0Middle Ordovician\u00a0units, and a source characterized by a substantial departure from equilibrium that could be associated with microbial methanogenesis. In contrast, methane from the Devonian-age Antrim\u00a0Shale, associated with less saline\u00a0porewaters, reveals \u0394<sup>13<\/sup>CH<sub>3<\/sub>D and \u0394<sup>12<\/sup>CH<sub>2<\/sub>D<sub>2<\/sub>\u00a0values that are approaching low temperature thermodynamic equilibrium. While microbial methanogenesis remains an important contributor to the methane budget in the Antrim Shale, it is suggested that Anaerobic\u00a0Oxidation\u00a0of Methane (AOM) could contribute to reprocessing methane isotopologues, yielding \u0394<sup>13<\/sup>CH<sub>3<\/sub>D and \u0394<sup>12<\/sup>CH<sub>2<\/sub>D<sub>2<\/sub>\u00a0signatures approaching thermodynamic equilibrium.<\/p>\n","protected":false},"template":"","tags":[],"publication_type":[19],"_links":{"self":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication\/14278"}],"collection":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication"}],"about":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/types\/publication"}],"wp:attachment":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/media?parent=14278"}],"wp:term":[{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/tags?post=14278"},{"taxonomy":"publication_type","embeddable":true,"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication_type?post=14278"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}